Surgical tourniquet cuffs typically are applied to a patient's limb at a desired location and are then pressurized in order to stop the flow of arterial blood past the cuff, thereby establishing a bloodless field in the portion of the limb distal to the cuff. The structure and function of some typical tourniquet cuffs of the prior art are described by Robinette-Lehmann U.S. Pat. No. 4,635,635, by Spence in U.S. Pat. No. 4,979,953 and by McEwen in U.S. Pat. Nos. 5,454,831 and 5,649,954. The pressure applied by such prior art tourniquet cuffs is typically controlled by electronic apparatus such as that described by McEwen in U.S. Pat. No. 4,469,099 and by McEwen and Jameson in U.S. Pat. No. 5,607,447.
The bloodless surgical field created by a pressurized tourniquet cuff facilitates many types of surgical procedures performed on upper limbs and lower limbs, helps improve the quality and consistency of the surgical procedures, reduces the need for blood transfusions, and shortens surgical times.
To reduce the probability of certain injuries to the soft tissues of the limb beneath a pressurized tourniquet cuff, some practitioners elect to apply a form of limb protection to the limb beneath the cuff. For example, in “Guideline for Care of Patients Undergoing Pneumatic Tourniquet-assisted Procedures,” published by the Association of periOperative Registered Nurses (AORN) in the United States in 2015, it is noted that “[a] low-lint, soft padding (e.g., limb protection sleeve, two layers of stockinette) should be placed around the limb according to the cuff manufacturer's instructions for use. The padding should be wrinkle-free and should not pinch the skin.”
In the prior art, soft bandages that have been used in conjunction with tourniquet cuffs have included sheet padding combined with a fluid-impervious layer and an adhesive tab as described by Hubbard in U.S. Pat. No. 4,406,281 as well as cast padding of the type wrapped around a broken limb before a cast is applied. Proper application of the soft bandages in conjunction with tourniquet cuff usage is very technique dependent, requiring a trained and experienced applicator. Further, some types of padding may release loose fibers when applied, and these fibers may enter the surgical field and may clog the hook-and-loop fasteners that are typically used to secure tourniquet cuffs in position around the limb, thereby reducing the effective strength of these fasteners and creating a potential hazard. Also, the padding itself may take on a non-uniform shape around the limb, especially when an overlying tourniquet cuff is inflated. Finally, if too much soft bandage is used or if it is applied improperly, then hazards may arise because the level of pressure required in the tourniquet cuff to stop blood flow past the cuff may increase substantially, and the position of the cuff on the limb may become unstable after inflation, increasing the likelihood that the cuff position may change significantly relative to the limb during use.
As an improvement to soft bandages and cast padding, tubular stockinette has also been used between the patient's limb and the tourniquet cuff. Typically, tubular stockinette is made and supplied in a wide range of predetermined “lay-flat” widths, knits and materials. Tubular stockinette consists of a knitted textile having a substantially cylindrical shape in which some of the knitted threads either are elastic or are knitted in a manner that permits elastic stretching of the tubular shape. In appearance, tubular stockinette resembles the ankle portion of a sock or the leg portion of a nylon stocking. Elastic threads are included in some types of tubular stockinette to give them stretch and elastic characteristics that are a function of the type and number of elastic and non-elastic threads used in the knit and the knit pattern itself. In other types of stockinette that are knitted from non-elastic threads, the stretch and elastic characteristics of the stockinette are primarily determined by the type of knit. Two general advantages of using tubular stockinette under a tourniquet cuff, in comparison to overlapping soft bandages, are (1) tubular stockinette does not shed loose fibers which can enter the surgical field and clog cuff fasteners, and (2) tubular stockinette does not produce as non-uniform a shape around the limb as can occur with soft bandages.
There are a number of limitations associated with such prior art tubular stockinette. The most important limitation is that the pressure applied to the encircled limb by the tubular stockinette may be too high or too low. If the tubular stockinette is stretched excessively to fit around the limb at the desired cuff location, too high a pressure may result. In such situations, the pressure applied to the limb by the elastically stretched tubular stockinette may be sufficiently high to stop the flow of venous blood out of the limb and impair the flow of arterial blood into the limb.
Such residual pressures are concerning, and manufacturers of cuffs and other tourniquet-related products emphasize that the deflated cuff and any underlying bandages should be completely removed as soon as tourniquet pressure is released, stating that even the slightest impedance of venous return may lead to congestion and pooling of blood in the operative field.
Alternatively, if the tubular stockinette is not stretched at all, or if it is not stretched sufficiently at a desired cuff location, then the tubular stockinette may apply no pressure to the underlying limb and inflation of an overlying tourniquet cuff may then produce folding and wrinkling of the tubular stockinette material. This can cause soft tissue injuries resulting from pinching, folding and shearing of skin beneath the tubular stockinette, as well as causing other hazards arising from local anomalies in the pressure applied to the limb beneath the tubular stockinette by the inflated cuff and from the increased inflation pressure that may be required in the cuff to stop blood flow.
The pressure applied by a tubular stockinette to a limb of a given shape, circumference and tissue composition can be measured using a biomedical pressure transducer, such as one described by McEwen in U.S. Pat. No. 4,869,265. Using such a transducer, it has been found in tests that pressures from 0 mm Hg to more than 60 mm Hg can be applied to limbs of varying circumferences and physical properties by prior art tubular stockinettes of varying sizes, materials, knits and designs. For comparison, it has been found that an applied pressure as low as 30 mm Hg can partially or completely obstruct venous blood flow, and that applied pressures lower than 60 mm Hg can impede and partially block arterial blood flow. It has been found in tests that the pressure of a snugly applied tourniquet cuff can be as high as 25 mm Hg.
Prior art limb protection sleeves described in U.S. Pat. No. 6,361,548 to McEwen (McEwen '548), U.S. Pat. No. 7,384,425 to McEwen (McEwen '425), and U.S. Pat. No. 7,909,849 to McEwen (McEwen '849), which are incorporated herein by reference, are matched to selected cylindrical tourniquet cuffs so that they apply a safe range of pressures within the circumference range of a selected cylindrical tourniquet cuff.
As the use of surgical tourniquets continues to grow, there is an increasing need to adapt tourniquet cuffs to the different and varying limb shapes encountered across the entire patient population. In some cases, a patient's limb can be generalized as being cylindrical in shape, but in most cases, patients' limbs are more accurately described as being non-cylindrical in shape and tapered, i.e. having a taper when viewed from one end of the area of application (such as the proximal end) to the opposite end (such as the distal end). Contour-type tourniquet cuffs and other approaches are used to adapt the tourniquet cuff to a non-cylindrical limb.
When tubular stockinette such as described in McEwen '548, McEwen '425 and McEwen '849, which has a uniform diameter and uniform stretch properties, is applied to a tapered limb, it can be difficult to achieve an appropriately uniform pressure over the length of the sleeve. The sleeve fits against the limb more tightly at its proximal end than at its distal end, so the portion of the limb within proximal end of the sleeve is subjected to greater pressure. As a result, in many cases the pressure exerted on the limb at the proximal end may exceed a maximum acceptable pressure. At the same time, particularly in the case of a limb having a substantial taper, the pressure exerted on the limb by the sleeve may be too low at the distal end (because the sleeve fits against the limb too loosely). That is, the pressure exerted on the limb by the sleeve at its distal end may be below a minimum acceptable pressure.
In addition, prior art limb protection sleeves may apply excessively high and unsafe pressures to a limb if the practitioner's technique is improper, in the case of soft bandage and cast padding limb protections, or if the practitioner selects an incorrectly matched limb protection sleeve, in the case of matching limb protection sleeves as described in McEwen '548, McEwen '425 and McEwen '849.
Furthermore, to avoid the need to pass the sleeve over the distal end of the limb, which may compromise the surgical site and increase the risk of infection, prior art limb protection sleeves require the use of an instrument (such as shears) to release the sleeve. This process increases perioperative workflow, complexity and time since the practitioner needs to find the appropriate instrument and may struggle with the cutting process while the sleeve is on the patient.
As a result, there is a need for a form of limb protection for use with tourniquet cuffs that overcomes prior art limitations and improves patient safety by: applying uniform pressure to tapered limbs, limiting the maximum pressure applied to the limb, reducing the risk of infection, and reducing perioperative workflow, complexity and time.